Fix set_blocking (#975) #1140

Job	Run time
Test CUDA support	47s
Rustfmt	13s
Test build-std (aarch64-tvos)	4m 22s
Test (stable)	27s
MSRV (ubuntu-latest)	21s
Test (beta)	27s
Test build-std (aarch64-tvos-sim)	2m 47s
MSRV (windows-latest)	51s
Test (nightly)	1m 16s
Test build-std (x86_64-tvos)	2m 31s
Test (linux32)	1m 27s
Test (macos)	2m 43s
Test (aarch64-macos)	53s
Clippy	8s
Test (aarch64-ios)	58s
Test (win32)	1m 16s
Test (win64)	2m 10s
Test (mingw32)	1m 12s
Test (mingw64)	1m 25s
Test (windows-2019)	3m 20s
Test (windows-aarch64, windows-latest, stable, aarch64-pc-windows-msvc, --no-run)	2m 19s
	31m 53s

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